Backplanes are frequently used in modular signaling, data processing or communication devices. Peripherals, plug-in cards or other functional modules which are provided with plug-in contacts can be inserted into the push-in rack. Running transverse to the push-in direction at the rear end of the push-in compartments of the push-in rack is the backplane which contains slots having plug connectors for each push-in compartment, the plug-in contacts of the peripherals which have been pushed in interacting with the plug connectors. A further plug connector for connection to the control apparatus for the peripherals which have been pushed in is available on the backplane. The plug connectors for the devices which have been pushed in are connected to the further plug connectors for the control apparatus via the backplane, this being able to be effected using either a bus-type parallel connection or a direct connection (point-to-point connection). Mixed structures in which for example power supply lines extending between the individual plug connectors are designed to be parallel in the manner of a bus and the data line, however, designed to be direct, are also conceivable.
In the field of data processing, such backplanes are frequently used if one or more identical peripherals (e.g., hard disk drives) are provided in a housing. Network service providers, in particular, frequently use server computers having a multiplicity of hard disk drives in the form of a RAID (Redundant Array of Independent Devices) system. If one hard disk drive fails, the arrangement of the drives in a push-in rack makes it possible to exchange the defective drive in a rapid and simple manner.
A lack of compatibility between the devices to be exchanged may constitute a problem. SAS (Serial Attached Small Computer System Interface) and SATA (Serial Advanced Technology Attachment) are, for example, two specifications for a high-speed data bus with serial data transmission. Systems and devices which are operated in accordance with one of these specifications (this is indicated below by placing the appropriate abbreviation in front) are frequently operated side by side in mixed environments in the field of servers. In this case, partially identical plug connectors are first of all provided for SAS and SATA systems. The basic features of the signal specifications of the two systems are similar but they differ in certain details, for example the signal amplitudes. The data format used is likewise different.
In this case, SAS control apparatuses usually have the additional capability of being able to process signals and data formats based on the SATA specification. Such SAS/SATA control apparatuses can thus work together with both SAS peripherals and SATA peripherals, whereas SATA control apparatuses can work together only with SATA peripherals. In contrast, the combination of an SATA control apparatus with an SAS peripheral does not work or does not work reliably.
In order to avoid such combinations which are not electrically compatible, the SATA specification provides a lug on the plug connector of the peripheral and a corresponding gap on the appropriate mating part, that is to say in the plug connector of a slot on a backplane, for example. SAS and SATA peripherals can thus be used on SAS backplanes but only SATA peripherals can be used in SATA slots. Although this mechanical protection makes it possible, in principle, to prevent an incompatible combination of peripherals and control apparatuses, it is associated with some disadvantages.
On the one hand, there is the risk of plug connectors and thus also the peripherals being destroyed if the mechanical barrier is overcome by an excessive expenditure of force, which can definitely occur in practice “when things are to be done quickly”. On the other hand, manufacturers of backplanes must provide them in the two versions. In addition, it must be ensured that, when operating systems, the respective version of the backplane used corresponds to the control apparatus being used. If, for example, the control apparatus is changed from SATA to SAS/SATA, the backplane must also be changed if an SAS-enabled peripheral is intended to be used. In contrast, if SAS backplanes are used, in principle, in order to circumvent this problem, there is again no protection against the incompatible combination of an SAS peripheral with an SATA control apparatus.
Particularly in the case of large systems having a large number of different servers and peripherals, for example in the case of the so-called server farms, in which very different hardware configurations are often used side by side and can also often change as a result of components being exchanged after a system failure, the mechanical solution is not suitable for protecting against inadvertently installed incompatible combinations.